The present invention relates generally to voltage regulators, and more particularly to control systems for switching voltage regulators.
Voltage regulators, such as DC to DC converters, are used to provide stable voltage sources for electronic systems. Efficient DC to DC converters are particularly needed for battery management in low power devices, such as laptop notebooks and cellular phones. Switching voltage regulators (or simply "switching regulators") are known to be an efficient type of DC to DC converter. A switching regulator generates an output voltage by converting an input DC voltage into a high frequency voltage, and filtering the high frequency input voltage to generate the output DC voltage. Specifically, the switching regulator includes a switch for alternately coupling and decoupling an unregulated input DC voltage source, such as a battery, to a load, such as an integrated circuit. An output filter, typically including an inductor and a capacitor, is coupled between the input voltage source and the load to filter the output of the switch and thus provide the output DC voltage. The switch is typically controlled by a pulse modulator, such as a pulse width modulator or a pulse frequency modulator, which controls the switch. A feedback circuit generates a control signal which controls the duty cycle of the pulse modulator in order to maintain the output voltage at a substantially uniform level.
In traditional switching regulators, the feedback controller continuously measures the output voltage and uses this measurement to continuously generate a control signal for the pulse modulator. Such a continuous feedback controller operates using analog circuits, such as resistors, capacitors and op-amps. Unfortunately, these analog circuits are expensive and/or difficult to fabricate as integrated circuits. Specifically, special techniques are needed to fabricate resistors in semiconductor devices. In addition, these analog circuits do not easily interface with any digital circuits that may be fabricated in the same semiconductor device.